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mistake, and that so far from the sponge being the fixed mass it is the glass rope which dips deeply into the mud or sand and forms a kind of anchor for the sponge head, probably being secreted by it for that purpose, and that it is not a mere growth attached parasitically to the sponge, but an essential part of its constitution. Professor Wyville Thompson has also been engaged in the capture and study of these forms, and has promised a memoir on the genus which is impatiently looked for by all interested in the subject. I have, not, however, heard of its appearance yet, and in the mean time, there are many points of interest and many structures of great beauty which we can discover for ourselves with a little expenditure of time and patience.
The sponge mass of the Hyalonema is perhaps most commonly cup shaped, with the glass rope attached to its inner concave surface. Sometimes it is more or less globular, with the glass rope running through it and attached to nearly the whole length of the long axis. As you see in the specimen before you, it is sometimes of considerable size, eight or nine inches in its longest diameter. It must be remembered that in a dried specimen such as those before us, just as is the case with the common sponge of our toilet table, what we see is the mere frame work or skeleton of the actually living sponge. During the life and growth of the sponge this skeleton is clothed with a soft semi-fluid gelatinous coating called sarcode, which is the really truly living matter of the organism; by which it breathes, by which is takes its food, by which it propagates and multiplies its species, and by which the skeleton, and the spicules of which I shall have something to say hereafter, are formed and secreted. Time will not admit of our discussion of this sarcode matter. I can only stay to remind you that it is not a mere homogeneous layer like a stratum of jelly, but that it contains an immense number of small sarcode cells or amœboid bodies, more or less globular in shape, often provided with a long whip-like filament or flagellum, by whose lashing movements currents of water are kept cir-
